Reproductive System
PLO P1 (414-417)
Male Reproductive System Anatomy
Organ
testes


seminiferous
tubules


interstitial cells


epididymis

ductus (vas)
deferens

prostate gland


Structure
male gonads suspended
within the scrotum
outside the abdominal
cavity
consists of lobules of
seminiferous tubules &
interstitial cells
one to three tightly
coiled tubules within
each lobule of the testes
collectively they measure
about 250 m in length
typical cell structure
found between the
seminiferous tubules (in
the lobules of the
testes)
coiled tube lying on the
dorsal and anterior
surface of the testes
within the scrotum
muscular duct that
curves around the
bladder & connects the
epididymis to the
ejaculatory duct
single doughnut-shaped
gland that surrounds the
upper portion of the
urethra just below the
bladder
has a duct that connects
to the urethra


Function
produce sperm
(note: this is done
exterior to abdominal
cavity to allow lower
temperature for better
sperm production)

site of spermatid
production
(spermatogenesis)

secrete androgens (ex.
testosterone)

site of maturation of the
spermatids into sperm
receives spermatids
from the seminiferous
tubules
stores sperm
stores sperm
receives sperm from the
epididymis and carries it
to the ejaculatory duct
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adds a basic fluid to
semen through a duct to
neutralize any acidic
urine left in the urethra
the prostate fluid helps
somewhat to nourish
sperm
Cowper's glands
(bulbourethral
glands)

pea-sized glands that lie
posterior to the
prostate on either side
of the urethra.


seminal vesicles

penis




urethra


two glands at base of the 
bladder, each with a duct
that joins with the vas
deferens to make the
ejaculatory duct
long shaft with an

enlarged tip (glans penis)
covered by the foreskin

(prepuce)
layer of connective
tissue under the skin
rich blood supply to
spongy erectile tissue
smooth muscle control of
blood flow

duct from the bladder
through the penis to the
urethral opening.
The urethra is joined by
a duct from the
prostate, the ejaculatory
duct, and a duct from
Cowper’s glands



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adds mucus-like fluid to
the urethra during
sexual intercourse to
assist in the lubrication
of coitus
also neutralizes any
acidic urine left in the
urethra
adds nutrients and fluid
to semen to nourish
sperm
organ of sexual
intercourse
erectile tissue fills with
blood when smooth
muscle (under autonomic
control) prevents blood
from draining from the
penis. This allows
conduction of sperm to
vagina through urethra
peristaltic contractions
move sperm and seminal
fluid through urethra
conducts sperm and
seminal fluid from the
ejaculatory duct
conducts seminal fluid
from the prostate
conducts seminal fluid
from Cowper’s glands
All go through the penis
to the urethral opening
Reproductive System
PLO P2 (414)
The path of sperm (=
)
Seminal Fluid Additions (=
)
(sperm does not pass through these
accessory glands)
urethral opening
Reproductive System
PLO P3 (414)
The seminal fluid makes up most of the 3.5 mL released during ejaculation.
There can be up to 400 million sperm in a single ejaculation.
Functions of Seminal Fluid



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seminal vesicle secretions provide a nutrient rich environment (fructose)
for sperm. Sperm have high energy demands because of their motility.
prostate gland and Cowper’s glands secretions’ create a basic environment
(pH = 7.5) to neutralize any acidic urine left in the urethra. Sperm
prefer a basic environment.
Cowper’s glands secretions’ and seminal vesicle secretions’ help lubricate
during coitus with the mucus-like fluids.
Seminal fluid contains prostaglandins which cause the uterus to contract
(some believe to help move sperm towards the egg, others believe it is to
move sperm away from the egg so only strongest sperm will reach the
egg)
Reproductive System
PLO P4 (416-417)
Sperm Structure
Part
tail
Structure
protein fibres –
resembles the
structure of a typical
flagellum
midpiece
an extension of the
cytoplasm which has
numerous mitochondria
head
the main part of the
cytoplasm of the cell
acrosome
a cap covering the head
of the sperm
Function
rhythmic contraction of
the protein filaments in
the tail causes a spirallike movement that
propels the sperm past
the surrounding fluids.
The mitochondria
respire sugars in the
seminal fluid to
generate ATP in order
to provide the energy
for movement of the
tail.
contains the nucleus
with it’s 23
chromosomes including
one X or Y chromosome
The acrosome contains
lytic enzymes which are
released when the
sperm reaches an ovum.
These enzymes digest
the outer membrane of
the egg, allowing
penetration of the
sperm.
Reproductive System
PLO P5 (417)
PLO P6 (417)
Male sex hormones
The interstitial cells of the testes produce androgens (male sex hormones)
including testosterone and androsterone. Testosterone is the main male sex
hormone.
Hormone control
 The interstitial cells of the testes are ultimately under the control of
the hypothalamus.

Recall: The hypothalamus is linked to the anterior pituitary gland by a portal system (two
capillary beds) where the hypothalamus releases a releasing hormone or a inhibitory hormone for
each of several hormones released from the anterior pituitary.

In this case, the hypothalamus releases gonadotropin-releasing hormone
(GnRH) that stimulates the anterior pituitary to secrete the
gonadotropic hormones: follicle-stimulating hormone (FSH) and luteinizing
hormone (LH)

In males:
- FSH promotes the production of sperm in the seminiferous tubules
and a hormone called inhibin.
- LH (aka: interstitial cell-stimulating hormone (ICSH)) controls the
production of testosterone by the interstitial cells.
-
These hormones work on a negative feedback system to regulate the
production of sperm and testosterone (ie. testosterone and inhibin
inhibit the release of LH and FSH from the anterior pituitary AND
release of GnRH from the hypothalamus)
Functions of testosterone:
 responsible for the development of the male sex organs
 brings about and maintains the secondary sexual characteristics that
appear during puberty.
- height (growth spurt)
- broad shoulders
- longer legs
- deeper voices (longer vocal cords)
-
hair on the face, chest, back
male pattern baldness
greater muscular development
building up and maintaining bone mass in men
NOT part of a PLO

-
Other functions:
Androgens influence fat distribution and deposition
Cognition – testosterone and other androgens are important in maintaining the wellbeing of the mind
Men with high testosterone levels are likely to be depressed or anxious
provides cardiovascular protection (lowers cholesterol)
improves energy level and mental alertness
enhances sex drive and sexual performance
increases red blood cell mass
promotes adequate sperm count
causes growth of penis during puberty
-
Low testosterone results in:
decrease in sex drive
fatigue and at times
anxiety and depression.
decreases in bone mass and may lead to osteoporosis which places these men at high
risk for fracture of bones, especially of the hip and spine.
enlargement of the breast area, known as gynecomastia.

-
Causes of low testosterone in adults includes:
Aging (testosterone level starts decreasing after the age of 40-45)
Pituitary tumor
Pituitary surgery / Radiation to the head area
Excessive alcohol drinking
Certain drugs, such as chemotherapy agents
Mumps
Testicular trauma
Testicular surgery ( rarely even after vasectomy)
Varicocele (a testicular condition)
Undescended or retractile testes
Chronic illnesses

-
Reproductive System
PLO P7 (418, 419)
Female Reproductive System Anatomy
Organ
Structure
ovaries
(female
gonads)

follicles

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
corpus
luteum

oviducts
(fallopian
tubes)

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small oval shaped structure on
each side of upper pelvic cavity
connective tissue layer that
surrounds many follicles and
corpus luteum
This is a structure within the
ovary. There are 3 stages a
follicle can be in
primary: immature diploid sex
cells stuck in prophaseI
surrounded with a simple
squamous epithelium
secondary: immature diploid sex
cell surrounded by stratified
cuboidal epithelium and some
follicular fluid
vesicular: built like a secondary
follicle except the cavities of
follicular fluid have begun to
balloon out and the diploid sex
cell divides in two and stops in
metaphase II (one big cell:
secondary oocyte, one small cell:
polar body)
Temporary gland-like structure
made of the epithelial cells of a
follicle after it has released it’s
oocyte from the ovary.
muscular tubes lined with cilia
that receive egg from the ovary
(not attached to ovary – egg
must cross gap)
oviducts have fimbriae that help
sweep egg into the oviduct after
ovulation
Function

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produces eggs
produces sex
hormones
estrogen and
progesterone
site of egg
maturation within
the ovary
produce estrogen
and some
progesterone
produces the
hormones
estrogen and
progesterone
move egg towards
the uterus
location of
fertilization
uterus
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cervix

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
vagina

thick-walled muscular organ
about the size of a pear (upside
down)
joined to the oviducts at it’s
anterior end
At it’s posterior end (the cervix)
it is joined to the vagina
lining is the endometrium which
forms part of the placenta
during pregnancy
endometrium has varying
thickness at different stages of
the uterine cycle
Most posterior portion of the
uterus
opening of uterus to the vagina dips down into the vagina
makes a 90 degree angle
between the uterus and the
vagina

single, elastic, muscular tube
that extends from the uterus to
the exterior of the body.
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clitoris

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found in the cleft between the
labia minora
an erectile structure comparable
to the penis that becomes
engorged with blood during
sexual arousal
rich in nerve endings

houses developing
foetus
site of
implantation
lining becomes
part of the
placenta which
exchanges
nutrients/gases
with foetus
constricts to
close the uterus
during foetal
development
dilates for birth
is beginning of
birth canal
(vagina)
receptacle for
sperm during
intercourse
part of birth
canal after feotal
development is
complete
centre of sexual
sensation in
females
Reproductive System
PLO P9 (421-423)
PLO P10 (421-424)
PLO P12 (424, 449, 450)
The Ovarian and Uterine cycles
The ovarian cycle drives the uterine cycle.
The Ovarian Cycle
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

A female is born with as many as 2 million follicles. There are only
300 000 to 400 000 left at puberty.
Only 400 will ever mature and be released from the ovary (ovulation).
The primary follicles all have a sex precursor cell that is halted in
metaphase I of meiosis.
The follicular phase
 The FSH from the anterior pituitary circulates in the blood and
promotes the development of a follicle.
 The follicle secretes estrogen and some progesterone during it’s
development.
 The circulating estrogen feeds back to the anterior pituitary and
slows the release of FSH (follicular phase will end)
 At the same time, the circulating estrogen feeds back to the
hypothalamus where it causes further release of GnRH in a spike at
the end of follicular development.
 Net result is that LH is still secreted from the anterior pituitary;
FSH is too but to a lesser degree (neg. feedback from estrogen)
Ovulation
 The high LH in the blood causes the fully developed follicle (vesicular
follicle) to release it’s egg on the 14th day of the 28 day cycle.
 The follicle matures to a secondary follicle and then to a vesicular
follicle when it ruptures and releases the egg within to the outside of
the ovary. This process is called ovulation.
 The follicle that remains on the inside of the ovary is then referred
to as the corpeus luteum.
Luteal phase
 LH continues to circulate and promotes development of the corpus
luteum that maintains estrogen and progesterone secretions.
 Progesterone causes the endometrium (lining of uterus) to build up
 As progesterone builds up, it has negative feedback over the anterior
pituitary secretion of LH.
 The result is the corpus luteum degenerates and the endometrium can
no longer build up and sloughs off (menstruation)
The Uterine Cycle
Driven by the events of the ovarian cycle.
A 28 day cycle that breaks down as follows:
Days 1-5
 Corpus luteum has just degenerated, so there’s low levels of estrogen
& progesterone.
 The endometrium disintegrates (blood vessels rupture)
 Menstruation occurs; day 1 is particularly heavy flow of blood and
tissues out of vagina.
Days 6-13 (proliferative phase)
 FSH builds in blood stream causing follicular development
 Developing follicle causes increase in blood estrogen concentration
 Endometrium thickens
Day 14
 Ovulation occurs
Days 15-28 (secretory phase)
 Increased production of progesterone by corpus luteum causes
endometrium to further increase thickness of endometrium
 Development and maturation of uterine glands (secrete thick mucuslike fluid)
 Endmetrium awaits implantation.
 If implantation does not occur, then the corpus luteum degenerates
and endometrium begins breaking down.
 If implantation occurs, then the forming placenta produces human
chorionic gonadotropin (HCG) which maintains the corpus luteum until
the placenta can make it’s own estrogen and progesterone which will
prevent the endometrium from disintegrating. (ie. No menstruation
during pregnancy)
Reproductive System
PLO P8 (423, 424)
PLO P11 (208, 394, 455, 458)
The main female sex hormone is estrogen.
The functions of estrogen
Estrogen promotes the release of GnRH from the hypothalamus during
follicular phase of ovarian cycle
Estrogen inhibits release of FSH from the anterior pituitary during
follicular phase of the ovarian cycle.
Estrogen is responsible for development of the secondary sexual
characteristics in females including:
fat distribution
body hair.
breast development
widening and deepening of the pelvic girdle.
The functions of Oxytocin
Oxytocin is an example of a hormone that has a positive feedback mechanism
During birth, sensory receptors in the cervix detect the baby’s head pushing
against it. When these nerve impulses reach the brain, the brain causes the
posterior pituitary to release oxytocin.
Oxytocin causes the uterus to contract pushing further against the cervix
and stimulating more receptors and thereby causing more oxytocin release.
Oxytocin also causes milk let-down during nursing. The more a baby suckles,
the more oxytocin is released (neural pathway) from the posterior pituitary
Menopause
 The cessation of ovulation due to the lack of responsiveness of the
ovaries to LH and FSH
 If menstruation is still occurring then it is still possible to conceive.
 Usually, the uterine cycle becomes irregular and a woman is not said to
be menopausal until she has not menstruated for a full year.
 Symptoms of menopause are:
– hot flashes
– dizziness
– headaches
– insomnia
– sleepiness
–
depression